Modeling and Experimental Analysis of Biogas in Diesel and Solid Oxide Fuel Cell Generators
thesisposted on 10.12.2012, 00:00 by Francesco Quesito
Biogas is a green fuel generally produced by agricultural or household waste, whose range of applications has become wider and wider in recent years. The present work aims to show how biogas may represent a precious alternative to conventional methane when feeding multiple types of machines apt to produce energy through both the traditional thermal machines, whose operation is based on a series of chemical reactions, and the innovative electrochemical generators, exploiting electrochemical reactions. On one hand, the first part presents an extensive Chemkin simulation analysis of biogas when involved in multiple combustion processes, with equilibrium composition, laminar premixed flames, and partially premixed flames (widely occurring in diesel generators) being the main topics to be covered. Flame structure, heat production, and emissions of pollutants are the main fields to be investigated, in order to point out how biogas may be capable to insure performances which are close to those of methane by considerably breaking down emissions at the same time. On the other hand, the second part includes a wide experimental analysis of biogas when directly feeding a tubular anode-supported fuel cell (SOFC) provided by Edison S.p.a. – Centro Ricerca e Sviluppo, Trofarello (Torino, Italy), as well as the implementation and validation of a numerical model (based on pre-existent literature) developed with Cantera and Matlab for predicting the final composition of the anode exhaust gases and the mole-fraction profiles of the main chemical species along the anode channel. Since SOFCs have the capability to internally reform biogas by mixing it either with carbon dioxide (dry reforming) or with water (steam reforming), the main intent is to analyze the cell chemistry and to evaluate the general effectiveness of biogas internal-reforming processes. Multiple experimental data have been acquired, in order to draw performance maps of the cell and to validate the numerical model by performing a deep exhaust-gas analysis, which has been carried out through the use of a gas chromatograph.